hey-Hey!!!,My 1990 is eating voltage regs. I scoped the battery looking for a shorted diode in the 3-phase bridge, but saw nothing useful( liddle ripples, all the same size ). I tried measuring the voltage reg case to batt negative voltage and got a steady 39 mV( black lead to batt, red lead to reg's case ).

Am tempted to start throwing parts at it, but I'd rather just fix what's broken, yes?cheers,Douglas

Run a wire lead from one of the mounting screws of the voltage regulator to the engine or the alternator. Also run another lead from the negative battery post to the rad support. You live in Michigan. Your truck has been subjected to many years and miles of corrosion to the point where your grounding to the cab and the regulator may have become intermittent.

Hello. I had a multi year issue of blowing voltage regulators. Narrowed it down to water intrusion. I started cutting the voltage regulators apart, and found that the wires within the regulator were not fully embedded in resin. They are embedded in sand and capped with resin. The stock location of the regulator facilitates the water intrusion. My fix (which has been great for 2 years now) entails moving the regulator under the passenger hood hinge. Applying silicone to the perimeter of the resin on the back side of the regulator, and silicone around the base electrical fitting. I live in a very very rainy place, this issue first showed its face when i moved here, and after finding the water in every one of my regulators led me to this fix.

The fix:Replace your ignition switch. All the power goes through it and they do wear out.Use the wire coming from the ignition switch to power a relay instead of directly to the regulator. Power the regulator through the contacts of the relay directly from the battery.Ground the regulator case.Clean every ground you can get at and use copper anti-seize between the contact points. This keeps corrosion out for a very long time.